Do not convert anything sensitive. Browser or services that collect analytics data might collect a copy of what you type here. You may use a command line tool like
# Encode to base64
echo 'phcco.com' | base64
# Decode
echo 'cGhjY28uY29t' | base64 --decode
# You may add a space before your command to avoid having the content saved in your history (.bash_history)
# Another alternative is to use files